AAON CB-024 Installation Operation & Maintenance

Contents

AAON CB-024 Installation Operation & Maintenance Manual pdf 18 page image

18Refrigerant Piping(See back of the manual for refrigerantpiping diagrams.)GeneralPiping from the condensing unit to the airhandler is the responsibility of the installingcontractor.Use only clean type “ACR” copper tubingthat has been joined with high temperaturebrazing alloy.The pipe or line sizes must be selected tomeet the actual installation conditions andnot simply based on the connection sizes atthe condensing unit or air handler.All CB Series condensing units are providedwith in-line shutoff valves on both the liquidand suction lines. These should remainclosed until the system is ready for start-upafter installation.Piping should conform to generally acceptedpractices and codes.Upon completion of piping connection, theinterconnecting piping and air handlerMUST BE evacuated to 500 microns or less;leak checked and charged with refrigerant.Determining Refrigerant Line SizeThe piping between the condenser and lowside must ensure:1. Minimum pressure drop, and2. Continuous oil return, and3. Prevention of liquid refrigerant slugging,or carryoverMinimizing the refrigerant line size isfavorable from an economic perspective,reducing installation costs, and reducing thepotential for leakage. However, as pipediameters narrow, pressure-reducingfrictional forces increase.Excessive suction line pressure drop causesloss of compressor capacity and increasedpower usage resulting in reduced systemefficiency. Excessive pressure drops in theliquid line can cause the liquid refrigerant toflash, resulting in faulty Thermal ExpansionValve (TXV) operation and impropersystem performance. In order to operateefficiently and cost effectively, whileavoiding malfunction, refrigeration systemsmust be designed to minimize both cost andpressure loss.REFRIGERANT PIPINGThis section is for information onlyand is not intended to provide alldetails required by the designer orinstaller of the refrigerant pipingbetween the condenser orcondensing unit and the air handlingunit. AAON, Inc. is not responsible forinterconnecting refrigerant piping.Consult ASHRAE Handbook –Refrigeration and ASME Standards.CAUTIONREFRIGERANT PIPINGLine sizes must be selected to meetactual installation conditions, notsimply based on the connection sizesat the condensing unit or air handlingunit.CAUTION